The differing influence of halides upon supramolecular aggregation through C-X...π interactions in the crystal structures of (5-methyl-1-(4-X- arylamino)-1H-1,2,3-triazol-4-yl)methanol derivatives, X = H, F and Cl

Article abstract of DOI:10.1039/c2ce25841b

The presence of localised C-X...π [or C-X...π(CC)] interactions are shown to be pivotal in the crystal structures of (5-methyl-1-(4-X-arylamino)-1H-1,2,3-triazol-4-yl)methanol derivatives, X = H (1), F (2) and Cl (3). In the absence of halide (1), molecules aggregate into supramolecular chains via alternating ten-membered {...HOC ₂N}₂ and 14-membered {...HN₂C ₃O}₂ synthons. Molecules assemble into a three-dimensional architecture via edge-to-face C-H...π(arene) interactions occurring between the phenyl rings. In the presence of halide (i.e. F (2) and Cl (3) in the 4-position of the phenyl ring), two-dimensional arrays are formed by interconnected ten-membered {...HOC₂N}₂ (as seen in 1) and 24-membered {...HO...NC₂OH...N ₄H}₂ hydrogen bonded synthons. The latter arrangement allows for the close approach of halide to the 1,2,3-triazole ring and the formation of C-X...π interactions which appear to be particularly significant in the case of Cl (3), as evidenced by systematic changes (i.e. elongation) in the geometric parameters within the five-membered ring. In this series of structures, the presence of C-X...π interactions is shown to moderate the supramolecular aggregation based on conventional hydrogen bonding. This journal is

Full text of DOI:10.1039/c2ce25841b

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PAPER
The differing influence of halides upon supramolecular aggregation through
…
C–X p interactions in the crystal structures of (5-methyl-1-(4-X-arylamino)-
1H-1,2,3-triazol-4-yl)methanol derivatives, X = H, F and Cl
Alessandro K. Jorda˜o,a Vitor F. Ferreira,a Anna C. Cunha,a James L. Wardell,bc Solange M. S. V. Wardell*d
and Edward R. T. Tiekink*e
Received 28th May 2012, Accepted 27th June 2012
DOI: 10.1039/c2ce25841b
…
…
The presence of localised C–X p [or C–X p(CLC)] interactions are shown to be pivotal in the
crystal structures of (5-methyl-1-(4-X-arylamino)-1H-1,2,3-triazol-4-yl)methanol derivatives, X = H
(1), F (2) and Cl (3). In the absence of halide (1), molecules aggregate into supramolecular chains via
…
…
alternating ten-membered { HOC2N}2 and 14-membered { HN2C3O}2 synthons. Molecules
…
assemble into a three-dimensional architecture via edge-to-face C–H p(arene) interactions occurring
between the phenyl rings. In the presence of halide (i.e. F (2) and Cl (3) in the 4-position of the phenyl
…
ring), two-dimensional arrays are formed by interconnected ten-membered { HOC2N}2 (as seen in
…
1) and 24-membered { HO NC2OH N4H}2 hydrogen bonded synthons. The latter arrangement
…
…
…
allows for the close approach of halide to the 1,2,3-triazole ring and the formation of C–X
p
interactions which appear to be particularly significant in the case of Cl (3), as evidenced by
systematic changes (i.e. elongation) in the geometric parameters within the five-membered ring. In
…
this series of structures, the presence of C–X p interactions is shown to moderate the
supramolecular aggregation based on conventional hydrogen bonding.
structure of ethyl (Z)-2-cyano-3-[(4-alkoxyphenyl)amino]prop-2-
enoate.4 In the crystal structure of this compound, rather than
…
Introduction
Directional and persistent conventional hydrogen bonding inter-
actions occurring between hydrogen atoms connected to electro-
negative elements remains as the mainstay of supramolecular
recognition, in particular in crystal engineering endeavours of both
organic and metal-organic molecules.1–3 However, it is also known
that such hydrogen bonding interactions may be usurped by less
conventional interactions as, for example, reported recently for the
putative N–H O hydrogen bonds, supramolecular aggregation
…
…
…
occurs through N p and O p interactions. While rare, the N p
interactions in this crystal structure were related to the well
5
…
established cation p interactions. Analogous interactions but
involving a lone pair interacting with a p-system, i.e. element(lone
…
pair) p, are attracting increasing attention. An early and
…
prominent example amongst these is the cytidine-O(lone pair)
p
(guanine) interaction that is thought responsible for stabilising the
structure of the left-handed Z-DNA duplex.6 It turns out that such
interactions are well documented in macromolecular chemistry7
but less well established in molecular crystallography.8,9 A focus of
aUniversidade Federal Fluminense, Departamento de Qu´ımica Orgaˆnica,
Instituto de Qu´ımica, Outeiro de Sa˜o Joa˜o Baptista, Nitero´i, RJ,
24020-141, Brazil
bFioCruz-Fundac¸a˜o Oswaldo Cruz, Instituto de Tecnologia em Fa´rmacos-
FarManguinhos, Rua Sizenando Nabuco, 100, Manguinhos, Rio de
Janeiro, RJ, 21041-250, Brazil. Fax: 55 21 2552-0435;
Tel: 55 21 2552-0435
…
recent studies of element(lone pair) p(arene) interaction interac-
tions has been upon the supramolecular aggregation patterns they
stabilise, for example in the crystal structures of transition metal
carbonyls10a as well as for heavier elements such as arsenic,10b
selenium,10c tellurium10d and lead.10e Halogen atoms are also
cDepartment of Chemistry, University of Aberdeen, Meston Walk, Old
Aberdeen, AB24 3UE, UK
dCentro de Desenvolvimento Tecnolo´gico em Sau´de (CDTS), Fundac¸a˜o
Oswaldo Cruz (FIOCRUZ), Casa Amarela, Campus de Manguinhos,
Av. Brasil 4365, 21040-900, Rio de Janeiro, RJ, Brazil.
E-mail: solangewardell@yahoo.co.uk
11
…
known to form C–X p(arene) interactions, including in the
realm of protein and protein/drugs structure,12 observations which
complements the propensity of halides to form X2 p interac-
…
eDepartment of Chemistry, University of Malaya, Kuala Lumpur, 50603,
Malaysia. E-mail: Edward.Tiekink@gmail.com; Fax: +60 3 7967 4193;
Tel: +60 3 7697 6775
tions.13 Based on surveys of the Cambridge Structural Database,14
2
…
both C–X p(arene) and X
…
p(arene) interactions are direc-
tional,15 and are the subject of increasing theoretical investiga-
tions.16 However, in terms of crystal engineering endeavours, the
…
{ Electronic supplementary information (ESI) available: Diagrams
showing molecular structures and crystallographic data. CCDC reference
numbers 882592–882594. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c2ce25841b
systematic utilisation of C–X p interactions as supramolecular
6534 | CrystEngComm, 2012, 14, 6534–6539
This journal is ß The Royal Society of Chemistry 2012

View Online
˚
synthons, operating in isolation of other supramolecular synthons,
is still in its infancy.17
…
Table 1 Selected geometric parameters (A, u) for 1–3
Parameter
(1)
(2)
(3)
The under-utilisation of the C–X p synthon in crystal
C1–O1
N1–N2
N2–N3
N3–N4
N1–C2
C3–N3
C2–C3
N1–N2–N3
N2–N3–N4
N2–N1–C2
N2–N3–C3
N4–N3–C3
N3–C3–C2
N3–N4–C5
O1–C1–C2–N1
N2–N3–N4–C5
1.4301(17)
1.3172(17)
1.3510(17)
1.3946(16)
1.3668(19)
1.3565(17)
1.376(2)
105.53(11)
121.45(11)
109.95(12)
112.60(12)
125.94(12)
103.47(12)
114.74(11)
68.12(17)
66.22(16)
1.423(2)
1.313(2)
1.348(2)
1.3828(19)
1.361(2)
1.360(2)
1.407(3)
1.352(3)
1.381(3)
1.438(3)
1.367(3)
1.359(3)
1.429(3)
108.30(18)
123.92(18)
107.71(19)
110.44(18)
125.56(19)
104.3(2)
118.52(17)
44.9(3)
engineering, in part, reflects a certain lack of understanding of
such interactions owing to a deficiency of systematic studies. This
deficiency clearly contradicts the first paradigm of crystal
engineering suggested by Desiraju,2 i.e. a pillar of crystal engineer-
ing is the systematic evaluation of closely related structures
designed to ascertain the influence upon crystal packing patterns
in response to small modifications to molecular structure - how
and why molecules pack as they do. In this spirit, herein, the crystal
and molecular structures of three compounds which differ only in
the substituent at the 4-position of the phenyl ring, Scheme 1, are
described. It will be demonstrated that a discernible influence upon
1.373(2)
105.45(14)
122.03(14)
110.10(14)
112.67(14)
125.29(14)
103.07(15)
116.46(13)
53.6(2)
…
crystal packing is related to the formation of C–X p interactions
80.3(2)
81.9(2)
in the halogen derivatives to complement previous studies in this
area showing that these interactions can be manifested in the
absence of supporting synthons.17 These new compounds became
available during investigations into evaluation of the anti-viral and
other biological activities of novel 5-methyl-1-(arylamino)-
1H-1,2,3-triazole derivatives.18
systematic elongation of the endo- and exo-cyclic N–N bonds as
well as the formally ethylenic bond, Table 1 is noted. This
observation is related to the supramolecular aggregation
patterns, specifically, the interaction of the 4-chloro substituent
with the 1,2,3-triazole ring, as described below.
Results and discussion
Supramolecular assemblies based on hydrogen bonding
Molecular structures
The common feature of the hydrogen bonding operating in the
…
The molecular structures of 1–3 are illustrated in Fig. S1 (see
ESI){ and key geometric parameters are collected in Table 1;
each structure comprises a single molecule in the asymmetric
unit. As the molecular structures bear a close similarity, the focus
of the description will be upon 1. The molecule comprises a five-
membered 1,2,3-triazole ring connected to a phenyl ring via a
secondary amine group. The phenyl ring is almost orthogonal to
the 1,2,3-triazole ring, forming a dihedral angle of 87.69(7)u (the
equivalent angles for 2 and 3 are 89.01(10) and 87.72(13)u,
respectively). Also connected to the five-membered ring are
methyl and hydroxymethyl substituents. Fig. 1 shows an overlay
diagram for the three molecules whereby the five-membered
rings are coincident. It is clear that the differences relate to the
torsion angles connecting the phenyl and hydroxymethyl
substituents to the central ring. From Table 1, the latter O1–
C1–C2–N1 torsion angles vary by about the 13u. Similarly, the
N2–N3–N4–C5 angles vary by nearly 15u. The relative homo-
geneity in the molecular structures indicates that successive
substitution of H in 1, for F in 2 and Cl in 3, does not
significantly influence the molecular conformation. However, a
systematic influence upon the geometric parameters is evident.
Referring to the canonical form shown in Scheme 1, the
geometric parameters describing the five-membered ring for each
of 1 and 2 are consistent with that shown. However, in 3 a
structures of 1–3 is the formation of O–H N1(triazole) and
…
amine–N4–H O hydrogen bonds. However, the hydrogen
bonding patterns are quite distinct, falling into two classes, i.e.
one adopted by 1 and the other by isostructural 2 and 3;
geometric details describing the intermolecular forces operating
in the crystal structures of 1–3 are listed in Table 2.
The hydrogen bonding in 1 leads to the formation of linear
supramolecular chains along the b-axis, Fig. 2a, comprising
…
alternating centrosymmetric ten-membered { HOC2N}2 and
…
larger centrosymmetric 14-membered { HN2C3O}2 synthons.
A consequence of this arrangement is that the five-membered
triazole rings are disposed to lie within the 14-membered rings
…
and so are orientated to form p p interactions which serve to
stabilise the supramolecular chains. A distinctive supramolecular
association is found in the structures of 2 and 3 which is related
to the direct intervention of the F and Cl substituents as
discussed below. In each of 2 and 3, the centrosymmetric 14-
…
membered { HN2C3O}2 synthons observed in 1 persist bringing
Scheme 1 Chemical structures and numbering scheme for the molecules
investigated herein: (a) 1 (Y = H) (b) 2 (Y = F), and (c) 3 (Y = Cl).
Fig. 1 Overlay diagram for molecules 1 (red), 2 (green) and 3 (blue)
drawn so that the five-membered rings are superimposed.
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a
…
˚
Table 2 Summary of intermolecular interactions (A–H B; A, u) operating in the crystal structures of 1–3
…
…
…
A–H B
A
H
B
A–H
H
B
A
B
Symmetry operation
(1)
O1
N4
C6
H1o
H4n
H6
H9
—
N1
O1
0.85(2)
0.89(1)
0.95
0.95
—
1.93(2)
1.99(1)
2.92
2.77
—
2.7751(18)
2.8753(18)
3.7390(19)
3.6074(18)
3.6329(13)
173(2)
171(1)
145
148
0
1 2 x, 12y, 12 z
1 2 x, 2y, 1 2 z
1 2 x, K + y, K 2 z
2x, 2K + y, K 2 z
1 2 x, 2y, 1 2 z
Cg(C5–C10)
Cg(C5–C10)
Cg(N1–N3,C2,C3)
C9
Cg(N1–N3,C2,C3)
(2)
O1
H1o
H4n
—
N1
O1
0.84(2)
0.89(2)
—
1.93(2)
1.93(2)
—
2.757(2)
2.814(2)
3.4435(11)
4.521(3)
170(2)
173(2)
0
2 2 x, K + y, K 2 z
2 2 x, 1 2 y, 1 2 z
2 2 x, 1 2 y, 1 2 z
1 2 x, 2K + y, K 2 z
N4
Cg(N1–N3,C2,C3)
C8
Cg(N1–N3,C2,C3)
Cg(N1–N3,C2,C3)
F1
1.367(2)
3.4497(18)
134.98(14)
(3)
O1
N4
C1
H1o
H4n
H1B
—
N1
O1
0.84(2)
0.88(2)
0.99
—
1.691(2)
2.00(2)
1.87(3)
2.80
—
3.4413(13)
…
2.835(3)
2.738(3)
3.401(3)
3.2843(15)
4.787(3)
169(3)
172(2)
120
0
134.90(9)
1 2 x, K + y, K 2 z
1 2 x, 1 2 y, 1 2 z
2 2 x, K + y, 1K 2 z
1 2 x, 1 2 y, 1 2 z
2 2 x, 2K + y, 1K 2 z
Cl1
Cg(N1–N3,C2,C3)
Cg(N1–N3,C2,C3)
Cg(N1–N3,C2,C3)
C8
Cl1
a
Cg corresponds to the ring centroid of the specified atoms, and the ‘‘A–H B’’ refers to the angle between the rings.
˚
range of values, i.e. short 3.096(3) A [C2] and 3.258(3) [C3] to a
two five-membered triazole rings close together enabling the
…
˚
long 4.022(2) A [N2]. It has been reported in the literature that
formation of p p interactions, see Table 2 for geometric details.
…
C–X atoms can approach an aromatic ring at various angles,11,17
nevertheless, can be directional.15 Terminology17b,20 describing
the different geometries of interaction seem to be uniformly
adopted,17 i.e. delocalised, semi-localised and localised when X is
perpendicular to the ring centroid, a specific bond and a
particular atom within the ring, respectively. On this basis, the
However, in these structures the O–H N1 hydrogen bonds occur
between dimeric aggregates related by glide symmetry along the
c-axis to generate 24-membered synthons incorporating six
…
hydrogen bonds, { HO NC2OH N4H}2. The result is the
…
…
formation of supramolecular layers in the bc-plane, Fig. 2b.
…
F(lone pair) p interaction in 2 might be best described as semi-
…
Three-dimensional architectures
localised or even as a F(lone pair) p(ethylene) interaction.
The chains in 1 pack into layers in the ab-plane. The pendent
phenyl rings inter-digitate along the c-direction allowing for the
…
As anticipated from their isostructural relationship, the Cl
…
atom in 3 forms similar interactions. The H Cl separation of
…
formation of edge-to-face C–H p(arene) interactions, whereby
˚
2.80 A is within the established distance criterion for an H Cl
each phenyl ring effectively bridges two other molecules thereby
stabilising a three-dimensional architecture, Fig. 3a. There are no
intermolecular connections between the phenyl groups and the
five-membered rings. In 2 (and 3), supramolecular layers stack to
enable inter-digitation of the phenyl rings where offset-face-to-
21
interaction of 2.95 A, and indicates a weak contact. What is
˚
…
remarkable is that the Cl ring centroid(N1–N3,C2,C3) distance
˚
of 3.4413(13) A is shorter that the analogous distance in 2 despite
˚
the considerable increase in size of Cl over F, i.e. 0.28 A. As for
2, the ring centroid distances span a range, short 3.154(3) [C2]
˚
and 3.401(3) [C3] to a long 4.004(2) A [N2], again consistent with
…
a Cl(lone pair) p(ethylene) interaction operating in isolation of
…
face p p interactions are evident between centrosymmetrically
˚
related rings. While the inter-centroid distance is 4.0504 (14) A,
i
pairs of C8 and C9 atoms interact with the C8 C9 separation
˚
being 3.455(3) A; symmetry operation i: 1 2 x, 1 2 y, 1 2 z. The
˚
comparable separation in 3 is 3.555(4) A. As opposed to the
…
supportive supramolecular synthons.
The tighter interactions in
3
are reflected in the
Kitaigorodsky’s packing index (as calculated in PLATON21) of
68.5 which is greater than 67.8 for 2. Further, the magnitude of
this interaction can be gauged from the influence upon the C2–
situation in 1, the halide substituents in 2 and 3 project out of the
phenyl-rich region to interact with the five-membered rings via
…
C–X p interactions, Fig. 3b.
˚
C3 bond distance which elongates to 1.429(3) A in 3 compared to
While the role of organic fluorine in supramolecular chemistry
attracts significant debate and remains controversial,19
˚
1.373(2) A in 2. This observation coupled with the fact that the
…
a
p
p interaction between the five-membered triazole rings in 3 is
definitive contribution of F to the stabilisation of the crystal
packing is evident in 2. As detailed in Fig. 4, the F atom is
proximate to a methylene-H atom and the five-membered 1,2,3-
significantly stronger than those in each of 2 and 1, as indicated
by the shorter ring centroid distance, Table 3, suggests
considerable sharing of electron density between the molecules
in 3 which concomitantly diminishes the electron density within
the five-membered five-membered triazole ring, Table 1.
…
˚
triazole ring. The H F separation of 2.68 A is just beyond the
…
established distance criterion for an H F interaction of
20
2.67 A, and probably contributes little to the stability of the
˚
crystal packing. However, it is acknowledged that distance/
significance correlations can be arbitrary and that naturally
interactions can and do persist, for example, beyond sums of van
Summary and conclusion
A compact supramolecular chain comprising alternating ten-
…
der Waals radii.10d,22 The F ring centroid(N1–N3,C2,C3)
…
membered { HOC2N}2 and 14-membered { HN2C3O}2 syn-
…
…
˚
distance is 3.4497(18) A but the F ring atom distances span a
thons is observed in the crystal structure of 1. The chains pack
6536 | CrystEngComm, 2012, 14, 6534–6539
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Experimental
Synthesis
Compounds 1–3 were obtained by reduction of the ethyl ester
precursor molecules.18a A solution of the desired ethyl ester
precursor18a (1.00 mmol) in anhydrous THF (5 mL) was added
drop-wise under a nitrogen atmosphere, to a LiAlH4 (2 mmol)
suspension in anhydrous THF (10 mL). The reaction mixture was
stirred at room temperature for 2 h after which water (10 mL) and
HCl (1 M) were added until pH = 1. The solution was stirred for a
few minutes and then extracted into dichloromethane (3x). The
organic extracts were combined, concentrated under reduced
pressure. The resulting residue was collected, washed with hexane/
dichloromethane (3:1) and dried under vacuum. The samples used
in the crystallographic study were grown from ethanol solutions.
(5-Methyl-1-(phenylamino)-1H-1,2,3-triazol-4-yl)methanol (1).
Obtained in 50% yield as a brown solid, m.p.: 197–198 uC.
Recrystallisation from EtOH produced colourless crystals. IR
(KBr) nmax (cm21) 3199 (N–H); 3128 (O–H). 1H NMR (300 MHz,
CDCl3): d 2.17 (s, 3H, CH3), 4.52 (d, 2H, J = 5.6 Hz, CH2OH),
5.13 (t, 1H, J = 5.6 Hz, CH2OH), 6.40 (dd, 2H, J = 1.0, 8.7 Hz,
arom.), 6.89 (tt, 1H, J = 1.0, 7.4 Hz, arom.), 7.21–7.25 (m, 2H,
arom.), 10.00 (bs, 1H, N–H) ppm. 13C NMR (75 MHz, CDCl3): d
6.9 (CH3), 54.8 (CH2OH), 112.6 (C-29 and C-69), 121.0 (C-49),
129.3 (C-39 and C-59), 131.8 (C-4 or C-5), 143.4 (C-4 or C-5), 146.7
(C-19) ppm. Anal. Calcd. for C10H12N4O: C, 58.81; H, 5.92; N,
27.43. Found: C, 58.25; H, 6.02; N, 27.48.
(5-Methyl-1-(4-fluorophenylamino)-1H-1,2,3-triazol-4-yl)metha-
nol (2). Obtained in 44% yield as a brown solid, m.p.: 178–182
uC. Recrystallisation from EtOH produced colourless crystals.
1
IR (KBr) nmax (cm21) 3207 (N–H); 3144 (O–H). H NMR (300
MHz, CDCl3): d 2.18 (s, 3H, CH3), 4.52 (d, 2H, J = 4.7 Hz,
CH2OH), 5.08 (t, 1H, J = 4.7 Hz, CH2OH), 6.44 (ddd, 2H, J =
2.0, 4.5, 8.9 Hz, H-29 and H-69), 7.04–7.11 (m, 2H, H-39 and
H-59), 9.96 (bs, 1H, N–H) ppm. Anal. Calcd. for C10H11FN4O:
C, 54.05; H, 4.99; N, 25.21. Found: C, 53.98; H, 4.93; N, 25.27.
Fig. 2 Supramolecular assemblies in 1 and 2 (and isostructural 3)
…
…
mediated by O–H N (orange dashed lines) and N–H O (blue dashed
lines) hydrogen bonding: (a) Linear supramolecular chain in 1, and (b)
Supramolecular layer parallel to the bc-plane in 2; hydrogen atoms
not involved in hydrogen bonding have been omitted for reasons of
clarity.
(5-Methyl-1-(4-chlorophenylamino)-1H-1,2,3-triazol-4-yl)metha-
nol (3). Obtained in 39% yield as a brown solid, m.p.: 189–190 uC.
Recrystallisation from EtOH produced colourless crystals. IR
(KBr) nmax (cm21) 3228 (N–H); 3118 (O–H). 1H NMR (300 MHz,
CDCl3): d 2.17 (s, 3H, CH3), 4.53 (d, 2H, J = 5.4 Hz, CH2OH),
5.10 (t, 1H, J = 5.4 Hz, CH2OH), 6.42 (d, 2H, J = 8.7 Hz, H-29 and
H-69), 7.28 (d, 2H, J = 8.7 Hz, H-39 and H-59), 10.10 (bs, 1H, N–H)
ppm. 13C NMR (75 MHz, CDCl3): d 6.9 (CH3), 54.8 (CH2OH),
114.3 (C-29 and C-69), 124.6 (C-49), 129.2 (C-39 and C-59), 131.8
(C-4 or C-5), 143.5 (C-4 or C-5), 145.6 (C-19) ppm. Anal. Calcd.
for C10H11ClN4O: C, 50.32; H, 4.65; N, 23.47. Found: C, 49.89; H,
4.80; N, 23.06.
into layers that sandwich the phenyl rings. The latter stabilise the
three-dimensional structure by self-associating via edge-to-face
…
C–H p(arene) interactions. For 2 and 3, to allow for the
…
participation of the halide atoms in C–X p interactions, two
key changes in crystal structure occur. Firstly, the chains in 1
…
are disrupted in that the compact 10-membered { HOC2N}2
synthons are substituted by more open 24-membered
…
…
…
{
HO NC2OH N4H}2 synthons so that layers are formed.
Secondly, the original pseudo layers in 1 (repeat distance = c/2 =
˚
10.51 A) are brought closer together in 2 and 3 (repeat distances
˚
= b = 6.64 and 6.63 A, respectively).
X-ray crystallography
…
Intensity data for 1 were measured at 150 K on a Rigaku
AFC12k/SATURN724 diffractometer fitted with MoKa radia-
tion. Data processing and absorption corrections were accom-
plished with CrystalClear23a and ABSCOR,23b respectively.
Intensity data for 2 and 3 were measured at 120 K on an
From the foregoing, it is likely that the C–X p interactions
are capable of moderating strong hydrogen bonding patterns in
the crystal structures of molecular compounds as has been noted
previously by others during crystal engineering studies of C–
11,15–17
…
H
X interactions.
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Fig. 3 Crystal packing in 1 and 2 (and isostructural 3): (a) View in projection down the b-axis of the unit cell contents of 1, and (b) View in projection
…
down the c-axis of the unit cell contents of 2. The O–H N, N–H O and p p interactions are indicated by orange, blue and brown dashed lines,
…
…
… …
respectively, and the edge-to-face C–H p (Fig. 3a) and C–F p (Fig. 3b) interactions are shown as purple dashed lines.
Enraf-Nonius KappaCCD area detector diffractometer (fitted
with MoKa radiation) of the EPSRC National crystallographic
service at the University of Southampton, UK.23c Data
collection was carried out under the control of the program
COLLECT23d and data reduction and unit cell refinement was
achieved with the COLLECT and DENZO23e software combi-
nation. Correction for absorption effects was by comparison of
the intensities of equivalent reflections as applied by the program
SADABS.23f Details of cell data, X-ray data collection, and
structure refinement are given in Table 3. The structures were
solved by direct-methods.23g Full-matrix least-squares refine-
ment on F2 with anisotropic displacement parameters for all
non-hydrogen atoms was performed.23g The C-bound H atoms
were placed on stereochemical grounds and refined with fixed
geometry, each riding on a carrier atom, with an isotropic
displacement parameter amounting to 1.2 times (1.5 times for
Table 3 Crystallographic data and refinement details for 1–3
Compound
(1)
(2)
(3)
Formula
C10H12N4O C10H11FN4O C10H11ClN4O
Formula weight
Temperature/K
Crystal system
Space group
204.24
150
monoclinic monoclinic
222.22
120
238.68
120
monoclinic
P21/c
P21/c
P21/c
˚
a/A
6.7842(19)
7.258(2)
21.155(6)
96.751(8)
1034.5(5)
4
1.311
432
0.090
13.4975(6)
6.6420(2)
13.8024(6)
120.480(3)
1066.39(7)
4
1.384
464
0.107
9414
13.4984(8)
6.6361(4)
14.0835(5)
118.380(3)
1109.93(10)
4
1.428
496
0.328
˚
b/A
˚
c/A
b/u
3
˚
V/A
Z
Dc/g cm23
F(000)
m(MoKa)/mm21
Measured data
h range/u
25 445
3.0–27.5
2363
15 735
2.9–27.5
2479
3.0–27.5
2434
2012
Fig. 4 Detail of the intermolecular interactions formed by the F atom in
Unique data
…
…
Observed data (I¢2.0s(I)) 2320
1694
2. The putative C–H..F, C–F p(ring) and C–F p(ethylene) interac-
tions are shown as grey, purple and black dashed lines, respectively. Non-
acidic hydrogen atoms not participating in these interactions are omitted
for reasons of clarity.
R, obs. data; all data
a; b in weighting scheme
Rw, obs. data; all data
0.053; 0.145 0.054; 0.111 0.048; 0.113
0.074; 0.298 0.021; 1.046 0.062; 0.567
0.053; 0.145 0.067; 0.120 0.086; 0.133
6538 | CrystEngComm, 2012, 14, 6534–6539
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Engineering, eds E. R. T. Tiekink and J. J. Zukerman-Schpector,
Wiley, Singapore, 2012, pp. 187–232.
methyl-H) the value of the equivalent isotropic displacement
parameter of the respective carrier atom. The O– and N–bound
H atoms were located in difference maps and refined with O–H =
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˚
0.84 ¡ 0.01 A and N–H = 0.88 ¡ 0.01 A, respectively, and with
˚
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2
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Acknowledgements
The X-ray data sets for 2 and 3 were collected at the EPSRC
X-ray Crystallographic Service, University of Southampton,
England; the authors thank the staff of the Service for help and
advice. The authors thank CNPq and FAPEMIG for financial
support. Support from the Ministry of Higher Education,
Malaysia, High-Impact Research scheme (UM.C/HIR/MOHE/
SC/12) is also gratefully acknowledged.
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